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Reply-To: bishop@php.net
Date: Fri, 26 Apr 2019 01:15:10 -0400
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To: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Revive Number Format Separator RFC
From: bishop@php.net (Bishop Bettini)

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On Thu, Apr 25, 2019 at 9:28 PM Bishop Bettini <bishop@php.net> wrote:

> On Thu, Apr 25, 2019 at 6:07 PM Theodore Brown <theodorejb@outlook.com>
> wrote:
>
>> Is there any chance the Number Format Separator RFC [1] could be revived
>> for PHP 7.4? I looked at the discussion from a few years ago and it's not
>> clear why many people originally voted against it.
>>
>> JavaScript and Python have both gotten this feature recently and it's
>> something I really miss in PHP when declaring/reading large numbers.
>>
>> Maybe it would help to simplify how the restrictions are described in the
>> RFC. As I understand it, the only restriction is that each underscore in a
>> numeric literal must be between two digits. Perhaps the way the RFC
>> described this syntax made it seem more complex than it is.
>>
>> Best regards,
>>
>> Theodore Brown
>>
>> [1]: https://wiki.php.net/rfc/number_format_separator
>
>
> Subsequent conversation occurred on the voting thread [1], which wasn't
> included by reference in the RFP itself.
>
> The only dissent I saw in that thread came from Pascal Martin, speaking
> for AFUP, who wrote [2]:
> > it would be harder to search in code, as there would be more than
> > one way to write a number. Basically, it would break grep/find.
> > Splitting numbers so they are more readable is kind of a presentation
> > matter and, as such, could be done by an editor/IDE when displaying
> > code, without having to modify the code by hand
>
> Related: the RFC author Tom Punt also detailed the implementation, but
> didn't incorporate that by reference into the RFC [3]. Worth the read.
>
> With Tom's blessing, I'd support re-visiting this feature. It's useful,
> IMO.
>
> [1]: https://marc.info/?l=php-internals&m=145271098232484&w=2
> [2]: https://marc.info/?l=php-internals&m=145320709922246&w=2
> [3]: https://phpinternals.net/articles/implementing_a_digit_separator
>

Using a variant of Nikita's top packages visitor [1], the top 250 packages
contain about 3 million integer literals. Of those, about 800k have 5 or
more digits, while only about 3k have 10 or more digits. Nine digits is
unusually common, because of its use in giggsey/libphonenumber-for-php for
United States phone numbers.

Applying some rough heuristics to file names, 89% of those literals appear
in a data file, 8% in code, and 3% in tests.

A cursory scan of current usage suggests that number format separator might
be used in scenarios such as:

Phone numbers
919_555_1234
49_89_636_48018

Date time values
2018_04_26
20180426_183242

Range end points (using any locale's grouping strategy)
2_147_483_647
1_67_77_215

Nibble groups
0b0011_1111_0100_1110

For those first few, Kotlin has similar examples [2], but Javascript
discourages use of number separator in "number-ish" values (eg phone
numbers) [3].

https://gist.github.com/bishopb/157d403dc1c190957a558c93e120a07d


[1]: https://gist.github.com/nikic/a2bfa3e2f604f66115c3e4b8963a6c72
[2]:
https://kotlinlang.org/docs/reference/basic-types.html#underscores-in-numeric-literals-since-11
[3]: http://2ality.com/2018/02/numeric-separators.html

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